The invention herein relates to a contact printer for use in reproducing precise duplicates of very large size drawings, which are engineered to exact final part size, and the like. In a number of different industrial or manufacturing procedures, i.e., product engineering, very large size, non-dimensioned drawings are used as tools from which templates, fixtures and so forth are made for final tooling. Non-dimensioned drawings are also used for sight gauges, industrial closed circuit numerical controls, and automatic drafting. For example, loft drawings used to lay out aircraft parts, ship parts and the like and automotive body drawings are typical of large size drawings which may be on the order of up to forty or even more feet in length and up to six feet in width and which are precisely drawn, but not dimensioned. In the manufacturing processes utilizing such drawings, the various parts are depicted on the drawing but are not dimensioned.
In the use of non-dimensioned drawings, the making of full size copies of the drawings is difficult because of the sizes involved. Moreover, it is difficult to make precision copies, i.e., copies that are precisely accurate reproductions of the original so that the copies may likewise be utilized for scaling purposes.
In the making of duplicates of original large size drawings, various copying techniques, including various photographic techniques have been used which utilize contact printing. That is, either photographic or other light sensitive film or sheet is placed in direct contact with the original drawing and the appropriate light is exposed upon the surfaces. The exposed film or sheet is thereafter processed, as for example by photographic development or the like, to produce the precision duplicate.
Ordinary reproducing machines or photcopy machines are not sufficiently accurate for reproductions of large size non-dimensioned drawings. Hence, in the past equipment has been used which, in essence, spreads out the original drawing in a flat stationary plane with the light sensitive film or sheet either above or below it, depending upon the process utilized. Then, a light source has been moved along the upper exposed surface, to shine the light in a manner such as to expose the film so that it may be processed into a finished copy. In certain of these processes, the photosensitive or light sensitive film or sheet is located below the drawing so that the light shining through the drawing exposes the sheet. In other processes, the light sensitive film or sheet is arranged above the drawing and by a bounce-back light arrangement, the copy is produced.
In the systems where the drawing and sheet are layed flat, upon a flat surface, a large size table-like support is needed. For example, a forty foot long drawing requires a support table of that length. Consequently, the equipment utilized for making drawings of this character ordinarily is very large and requires a great deal of building space. In addition, the equipment is relatively cumbersome to use and requires a considerable amount of labor and time to produce the required copies.
An example of a long, flat bed printer is illustrated in my prior patent U.S. Pat. No. Re. 28,770, reissued Apr. 13, 1976 for a photographic exposure apparatus, the original patent number being U.S. Pat. No. 3,723,001 issued Mar. 27, 1973. Other examples of conventional flat type printers are illustrated in U.S. Pat. No. 2,427,923 issued to Reynolds on Sept. 23, 1947 for an apparatus for printing on light sensitive material. Other patents showing similar types of flat bed contact printers are illustrated in U.S. Pat. No. 2,919,635 to Levine on Jan. 5, 1960 for "Printing Exposure Machine for Photosensitive Materials", U.S. Pat. No. 2,988,979 issued to Siegler on June 20, 1961 for "Exposure Apparatus for Photosensitive Materials", U.S. Pat. No. 4,182,569 issued to Smith on Jan. 8, 1980 for a lithographic dual light source apparatus, and British Pat. No. 1,116,151 published June 6, 1968 for improvements in photomechanical printing apparatus invented by Milborne.
Efforts have been made to eliminate the large size support tables and instead to utilize a roll type system where the drawing and sensitized sheet are moved through more compact equipment. However, where rollers have been used the curvature of the sheet around the rollers tends to produce inaccuracies which increase depending upon the length of the sheet. Thus, systems whereby the sheet or drawing are curved during the light exposure are not satisfactory to produce precision drawings.
Thus, in my prior application, Ser. No. 010,628 filed Feb. 9, 1979 now U.S. Pat. No. 4,212,533 for a "Photographic Exposure Apparatus", I disclose a compact contact printer which utilizes a belt support system upon which overlapped sensitized sheets and drawings may be fed for movement beneath stationary light sources. A vacuum system is provided to clamp the drawing and sheets together during the light exposure.
Vacuum systems, as well as various types of electrostatic systems have been used in the prior, long flat table type of exposure units. However, the prior vacuum systems, as well as the electrostatic systems for holding the sheet and drawing together during exposure, have not been adequate in a compact form of equipment.
Examples of similar types of contact printing equipment which utilize electrostatic means for holding the sheet and drawing together, as contrasted with the above mentioned patents which for the most part utilize vacuum systems for that purpose, are illustrated in U.S. Pat. No. 3,844,657 issued Oct. 29, 1974 to Schweriner for a "Contact Printing Apparatus and Method" and in U.S. Pat. No. 3,888,586 issued to Arden and Schweriner on June 10, 1975 for a "Contact Printing Apparatus with Electrostatic Hold Down".
In the equipment of my above mentioned application, the vacuum system utilized is relatively expensive, utilizing a perforated support belt beneath which a vacuum source is positioned for holding the sheet and drawing upon the support belt during exposure times.
Thus, the invention of this present application relates to a vacuum system support belt which is relatively inexpensive and efficient to rapidly flatten out the drawing and sheet, i.e., to eliminate bends or curves or wrinkles therein, and to hold the sheets in flat condition, and in tight surface to surface contact, during exposure thereof. In my prior system, although the sheet and drawing are held in tight contact, flattening out the sheet and drawing in certain instances is relatively difficult. Thus, the present invention relates to an improvement over my prior printer.